The drop is in line with everything else dropping, but for PS4 it's special? And really. 10K is all Sony can deliver? Last year they could deliver 20K. Have Sony factories exploded or what?
My theory is that they are trying to force a customer purchase shift towards the Pro Model as a natural progression from the older Units just as the Old 3DS faded away as the N3DS gained traction. They probably just haven't got the ratios right yet.